1. Field of the Invention
The present invention relates to a suspension board assembly sheet with circuits and a method for manufacturing the same.
2. Description of the Background Art
Actuators are employed in drives such as hard disk drives. Such an actuator includes an arm arranged rotatably with respect to a rotation shaft and a suspension board with a circuit (hereinafter, abbreviated as a suspension board) for a magnetic head that is attached to the arm. The suspension board is a printed circuit board for positioning the magnetic head with a desired track of a magnetic disk.
The suspension board is provided with the magnetic head, and connected to another electronic circuit. Conductor traces are formed on the suspension board, and electrical signals are transmitted between the another electronic circuit and the magnetic head through the conductor traces.
A method for mass production of such a suspension board is suggested, where the processes for formation of an insulating layer, conductor traces, and a cover layer are sequentially applied to a long-sized substrate which is continuously or intermittently transported by rollers (see JP 2001-101639 A, for example).
A plurality of suspension boards are formed on the long-sized substrate in the manufacturing process of the suspension boards in JP 2001-101639 A. An assembly of the plurality of suspension boards (hereinafter referred to as an assembly sheet) that is produced as a half-finished product is subjected to inspection for detecting defects (disconnections, short-circuits or the like) in the conductor traces of each suspension board.
Continuity test, automatic optical inspection (AOI), and visual check, for example, of the conductor traces are performed for detecting defects in the conductor traces of the assembly sheet.
For example, the AOI is performed in the following manner. First, the conductor traces in a good state with no defects are imaged by an imaging device, and the obtained image data is stored in a memory as master data. Then, the conductor traces formed on the assembly sheet are imaged by the imaging device, and the obtained image data is stored in the memory as inspection target data. The master data and the inspection target data are subsequently compared with each other, so that the presence/absence of defects in the conductor traces formed on the assembly sheet is determined.
Since the determination obtained through the AOI has limitations in terms of accuracy, the visual check following the AOI is further performed by a worker. However, the visual check puts a heavy burden on the worker and increases inspection cost. Therefore, it is required that the determination accuracy of the AOI is improved to decrease the burden on the worker and the inspection cost.